Microplastics in the brain: how they get there and what are the risks

Every sip you take from a plastic straw not only contributes to environmental pollution, but could also be leaving tiny particles in your body, even your brain.

A recent study published in Nature Medicine has revealed alarming evidence of the accumulation of microplastics in vital human organs . This revelation came just days before US President Donald Trump signed an executive order to reverse the ban on plastic straws and eliminate paper ones.

Microplastics are plastic particles that measure less than 5 millimetres in diameter . So-called nanoplastics are even smaller, measuring less than a micrometre (one thousandth of a millimetre). Because of their tiny scale, they have the ability to cross biological barriers: it is estimated that an average person could ingest tens of thousands of microplastic particles per year.

Microplastics and nanoplastics have been detected in virtually every ecosystem on the planet, from the oceans to the air we breathe. Their main sources include plastic waste in the environment, such as bottles, straws, bags and packaging , which over time break down into tiny particles.

Synthetic clothing , made from materials such as polyester and nylon, releases plastic microfibres with every wash, shedding hundreds of thousands of these fibres in a single load of laundry. They are also present in some personal care products, such as exfoliants, toothpastes and cleansers that contain plastic microbeads.

Another important source is the wear and tear of car tyres , which releases plastic particles onto roads. In the maritime sphere, fishing nets, ropes and other plastic equipment degrade in the ocean, generating microplastics that affect marine fauna and eventually enter the food chain.

In addition, food packaging and plastic bottles can produce tiny particles over time, contaminating what we consume. Even urban air contains microplastics suspended in dust, which means we also inhale them on a daily basis.

Microplastics can enter the body through food and water intake, inhalation of airborne particles, and possibly absorption through the skin. The most studied route is ingestion, as these contaminants have been detected in bottled and tap water, in seafood and fish that ingest them from the environment, in table salt, and even in fruits and vegetables that can absorb plastic particles through soil and irrigation water.

In addition, the use of plastic containers and utensils to store or heat food can transfer nanoparticles to what we consume.

Inhalation is another route of exposure. Synthetic fibres in clothing, indoor dust and emissions from tyre friction on roads can release tiny particles. Microplastics have been found in the lungs of living people, suggesting they can lodge in the respiratory system and, in some cases, migrate into the bloodstream and reach other organs.

Although the specific effects on the respiratory system are still being studied, the presence of these particles in the lungs raises concerns about possible inflammatory reactions and respiratory problems.

Finally, although the skin is an effective barrier, some studies have raised the possibility that smaller nanoplastics may be able to pass through it, especially if there are wounds or if they are found in cosmetic products such as creams and exfoliants.

There is also concern that contact with water contaminated by microplastics, such as oceans and rivers, may be another source of dermal exposure. However, evidence on penetration by this route is still limited.

Once inside the body, microplastics can enter the bloodstream and reach vital organs such as the liver, kidneys and heart.

The brain, protected by the blood-brain barrier, has traditionally been considered a safe environment against many toxins, external particles and microorganisms. However, the research cited has revealed that certain nanoplastics , due to their tiny size and chemical composition, can reach brain tissue .

Indeed, recent data indicate that microplastic concentrations in the brain may be higher than in other organs, suggesting a preferential accumulation or reduced clearance capacity in this region. It has been proposed that transport of these particles may occur through the bloodstream or even by migration along the olfactory nerve from the nasal cavity .

Once these particles cross the blood-brain barrier, they can alter cellular balance and trigger adverse responses. The main mechanisms involved include oxidative damage and cellular stress, inflammation and activation of the immune system, as well as possible associations with neurodegenerative diseases such as dementia .

Data from the study published in 'Nature Medicine' indicate that microplastics can generate a pro-oxidant environment in the brain , promoting damage to proteins, lipids and neuronal DNA. This can compromise the integrity of brain cells, alter neuronal signaling and predispose to cell death.

In addition, some particles contain chemical additives that can interfere with fundamental cellular processes. Exposure to these substances has been observed in animal models to alter synaptic plasticity and affect cognitive function.

The presence of microplastics in the brain appears to chronically activate microglia cells, which are specialized in the brain's immune response, triggering a sustained inflammatory response. The cited research suggests that elevated levels of these particles may increase markers of inflammation, which could contribute to progressive neuronal deterioration and the alteration of neural circuits essential for memory and learning.

One of the most worrying findings in research on microplastics is their possible relationship with neurodegenerative diseases, since their concentration was higher in the brains of people with dementia.

Although it has not been determined whether there is a causal relationship between microplastics and dementia in humans, chronic inflammation, oxidative stress and disruption in neuronal communication are key mechanisms in neurodegenerative diseases such as Alzheimer's and Parkinson's .

While the human body has natural mechanisms for detoxifying and removing foreign substances, such as the lymphatic system and liver and kidney processes, it is unclear to what extent they can handle microplastics. The most effective strategy currently is to minimize exposure.

Given the growing concern about the presence of microplastics in food, especially in seafood, should we then stop eating fish and seafood? Definitely not. They are essential sources of protein, omega-3 fatty acids and other key nutrients for brain and cardiovascular health.

However, we can reduce the intake of microplastics from these products. For example, it is advisable to wash fish well and remove its digestive tract and abdomen before eating it, since these tissues accumulate more microplastics. Opting for smaller fish , such as sardines and anchovies, is another good strategy, since large specimens tend to accumulate more contaminants along the food chain.

It is also important to choose sustainably sourced products with certifications that prioritize ocean health, avoid the consumption of filter-feeding shellfish such as mussels and oysters, and prefer plastic-free packaging.

Secondly, to minimise the risk of inhalation, it is recommended to use high-performance air purifiers capable of capturing suspended particles, avoid heating food or liquids in plastic containers and reduce the use of synthetic textiles such as polyester and nylon. Opting for natural fibres such as cotton, wool and silk can be a safer alternative. It is also advisable to vacuum dust instead of sweeping and to dispose of plastic waste properly.

At the individual level, additional measures include reducing the use of plastic cups and straws, avoiding toys with a high plastic content, minimizing the consumption of ultra-processed foods, and promoting education about the environmental impact of plastics.

From a more global perspective, reducing microplastic pollution requires changes at the level of policies and consumption practices. Promoting sustainable fishing practices and using guides such as Seafood Watch can help to choose safer sources of seafood.

Supporting a ban on single-use plastics and encouraging the use of recycled materials from ocean waste can also help reduce the amount of microplastics in ecosystems and, ultimately, in our bodies.

Ultimately, recent findings on the presence of microplastics in human organs reinforce an undeniable reality: these particles are everywhere and can infiltrate biological systems with as yet unknown consequences. A joint effort between the scientific community, policy makers and the general public is essential.

However, measures such as those enacted in the United States seem to go in the opposite direction. The question is no longer whether microplastics are in our bodies, but what we are prepared to do about it.

This article was originally published on The Conversation .